阅读说明：本技术 衍射光学元件及其制备方法、屏下光学系统及电子设备 (Diffractive optical element, manufacturing method thereof, optical system under screen and electronic equipment ) 是由 鞠晓山 冯坤亮 李宗政 于 2020-07-21 设计创作，主要内容包括：本申请提供一种衍射光学元件制备方法,使用了迭代傅里叶转换分析法,实现了消减光线穿过透明显示屏时的高阶衍射。本申请还提供一种使用该方法制备的衍射光学元件、一种具有该衍射光学元件的屏下光学系统及一种电子设备。本申请通过使用迭代傅里叶转换分析法得出衍射光学元件的物理单元参数,使得该衍射光学元件能够消减光线穿过对应的透明显示屏时发生的光学衍射效应,进而提升了影像质量。(The application provides a method for manufacturing a diffractive optical element, which uses an iterative Fourier transform analysis method to reduce high-order diffraction when light rays pass through a transparent display screen. The application also provides a diffractive optical element prepared by using the method, an optical system under a screen with the diffractive optical element and an electronic device. This application obtains the physical unit parameter of diffraction optical element through using the iterative Fourier transform analytic method for this diffraction optical element can subdue the optical diffraction effect that takes place when light passes corresponding transparent display screen, and then has promoted image quality.)

1. A method of manufacturing a diffractive optical element, comprising the steps of:

s1: acquiring a two-dimensional screen penetration distribution map, and adding a random phase to obtain a first space domain, wherein the two-dimensional screen penetration distribution map is a distribution map of the light penetration rate of each microstructure of the two-dimensional screen;

s2: transforming the first spatial domain into a frequency domain by a fourier transform;

s3: reducing higher order diffraction in the frequency domain by low pass filtering;

s4: converting the low-pass filtered frequency domain into a second spatial domain by an inverse Fourier transform;

s5: judging whether the frequency component of the second spatial domain converges to a preset cut-off frequency range, wherein the cut-off frequency is a standard deviation sigma of normal distribution, if so, executing step S7; if not, go to step S6;

s6: adding a random phase to the second spatial domain to convert the second spatial domain into a new first spatial domain, and performing step S2;

s7: and converting the physical unit parameters of the diffraction optical element according to the second space domain, and processing physical units on the substrate by using a wafer level process according to the physical unit parameters to obtain the diffraction optical element.

2. The method for producing a diffractive optical element according to claim 1, wherein the fourier transform formula in step S2 is:

where ξ is a frequency domain, i is an imaginary number, and ω is a spatial domain;

the formula of the inverse fourier transform in step S4 is:

3. the diffractive optical element production method according to claim 1, wherein the formula for reducing the higher order diffraction by the low pass filtering in step S3 is:

where (x, y) is the coordinate of the frequency domain in the frequency space, and σ is the standard deviation of the normal distribution.

4. The method for producing a diffractive optical element according to claim 1, wherein the formula for converting the physical unit parameters of the diffractive optical element according to the second spatial domain in step S7 is:

Φ＝2π(n₀-n)d/λ；

where Φ is the spatial domain phase, n₀The refractive index of air, n the refractive index of the material of the diffractive optical element, d the depth of the structure of the physical unit, and λ the wavelength.

5. A diffractive optical element, comprising:

a substrate; and

the physical units are arranged on at least one side of the substrate through a wafer-level process and used for reducing high-order diffraction;

the parameters of the physical unit are determined according to the method for manufacturing a diffractive optical element according to any one of claims 1 to 4.

6. The diffractive optical element according to claim 5, characterized in that said diffractive optical element is first, second, fourth or eighth order.

7. The diffractive optical element according to claim 5, characterized in that the physical elements have a structure depth in the range of 0.2 μm to 1 μm, a line width in the range of 0.5 μm to 4 μm, and a registration accuracy of the physical elements at corresponding positions on the substrate in the range of ± 1.5 μm.

8. An underscreen optical system, comprising:

a transparent display screen including a plurality of pixel units arranged periodically for display;

the optical module is used for receiving the light beams from the transparent display screen or emitting light beams outwards through the transparent display screen; and

the diffractive optical element according to any one of claims 5 to 7, disposed between said transparent display screen and said optical module.

9. The underscreen optical system of claim 8 in which the gap between the diffractive optical element and the transparent display screen is in the range of 0 μ ι η to 5 μ ι η.

10. An electronic device, comprising:

a body; and

the underscreen optical system of any one of claims 8 or 9.

Technical Field

The invention relates to the technical field of optics, in particular to a diffractive optical element and a preparation method thereof, an optical system under a screen and electronic equipment.

Background

At present, the requirement of consumers on the display effect of a display screen of electronic equipment such as a smart phone is higher and higher, but due to the influence of diffraction effect, miscellaneous spots can appear on the display screen, and the picture effect is influenced. To eliminate the effects of diffraction effects, an optical compensation element is typically attached under the display that can counteract some of the effects of diffraction.

In the process of implementing the present application, the inventor finds that the following problems still exist in the prior art: under the influence of high-order diffraction effect and different light angles of the display, the offset effect of the existing compensation element on the diffraction effect is not ideal.

Disclosure of Invention

In view of the above, it is desirable to provide a method and an apparatus for manufacturing a diffractive optical element to solve the above problems.

A method of manufacturing a diffractive optical element, comprising the steps of:

s1: acquiring a two-dimensional screen penetration distribution map, and adding a random phase to obtain a first space domain, wherein the two-dimensional screen penetration distribution map is a distribution map of the light penetration rate of each microstructure of the two-dimensional screen;

s2: transforming the first spatial domain into a frequency domain by a fourier transform;

s3: reducing higher order diffraction in the frequency domain by low pass filtering;

s4: converting the low-pass filtered frequency domain into a second spatial domain by an inverse fourier transform;

s5: judging whether the frequency component of the second spatial domain converges to a preset cut-off frequency range, wherein the cut-off frequency is a standard deviation sigma of normal distribution, if so, executing step S7; if not, go to step S6;

s6: adding a random phase to the second spatial domain to convert the second spatial domain into a new first spatial domain, and performing step S2;

s7: and converting the physical unit parameters of the diffraction optical element according to the second space domain, and processing physical units on the substrate by using a wafer level process according to the physical unit parameters to obtain the diffraction optical element.

The method uses an iterative Fourier transform analysis method to process a spatial domain, and the purpose of multiple iterations is to filter the high-order diffraction point by point, so that the filtering effect is poor if the high-order diffraction is filtered to the cut-off frequency once, and the reduction effect of the high-order diffraction cannot be completely matched with the pixel unit of the screen. Through a plurality of iterations, the high-order diffraction is gradually filtered out until the frequency component of the second spatial domain converges into the cut-off frequency, and then the spatial domain with better high-order diffraction filtering condition can be obtained, so that the converted physical unit parameters are more accurate, and the high-order diffraction reduction effect corresponding to the diffractive optical element is better.

Further, the formula of the fourier transform in step S2 is:

where ξ is a frequency domain, i is an imaginary number, and ω is a spatial domain;

the formula of the inverse fourier transform in step S4 is:

according to a Fourier transform formula, the conversion from the first space domain to the frequency domain can be completed; the low-pass filtered frequency domain is re-converted to a new spatial domain by performing an inverse fourier transform, and is a second spatial domain distinct from the first spatial domain.

Further, the formula for reducing the higher order diffraction by low pass filtering in step S3 is:

where (x, y) is the coordinate of the frequency domain in the frequency space, and σ is the standard deviation of the normal distribution.

The low-pass filter is in two-dimensional normal distribution, and the center of the low-pass filter is placed in the center of a frequency domain and then multiplied by the frequency domain, so that high-order diffraction can be filtered.

Further, the formula of the conversion into the physical unit parameters of the diffractive optical element according to the second spatial domain in step S7 is:

Φ＝2π(n₀-n)d/λ；

where Φ is the spatial domain phase, n₀The refractive index of air, n the refractive index of the material of the diffractive optical element, d the depth of the structure of the physical unit, and λ the wavelength.

After the second space domain and the multiple parameters are substituted into the formula, the structural depth of the physical units can be obtained, and the number of the physical units can be a plurality of corresponding units because the screen is provided with a plurality of pixel units. And processing the physical units on a substrate by using a wafer-level process according to the obtained parameters of the physical units so as to obtain the diffractive optical element, wherein the diffractive optical element is matched with a screen for use.

A diffractive optical element comprising:

a substrate; and

the physical units are arranged on at least one side of the substrate through a wafer-level process and used for reducing high-order diffraction;

the parameters of the physical unit are determined according to the above-mentioned method for manufacturing the diffractive optical element.

Further, the diffractive optical element is first, second, fourth, or eighth order.

In various embodiments, the diffraction efficiency is multiplied as the order is increased.

Further, the structural depth range of the physical unit is 0.2-1 μm, the line width range of the physical unit is 0.5-4 μm, and the alignment precision range of the corresponding position of the physical unit on the substrate is ± 1.5 μm.

In the range, the physical unit has a good high-order diffraction reduction effect, and meanwhile, the normal propagation of light rays cannot be excessively influenced; the pixel units in the transparent display screen can be well matched, and the corresponding high-order diffraction reduction effect is more accurate; the high-order diffraction reduction effect on the transparent display screen 20 can be better satisfied.

An underscreen optical system comprising:

a transparent display screen including a plurality of pixel units arranged periodically for display;

the optical module is used for receiving the light beams from the transparent display screen or emitting light beams outwards through the transparent display screen; and

the diffractive optical element described in any of the above embodiments is disposed between the transparent display screen and the optical module.

The optical system under the screen can reduce the high-order diffraction aiming at the light rays which pass through the display screen by the transmitting module or the receiving module.

Further, the gap between the diffractive optical element and the transparent display screen is in the range of 0 μm to 5 μm.

Within this range, the diffractive optical element can achieve a good effect of reducing higher-order diffraction.

An electronic device, comprising:

a body; and

the underscreen optical system of any of the above embodiments.

According to the diffractive optical element, the preparation method thereof, the under-screen optical system with the diffractive optical element and the electronic device, the physical unit parameters of the diffractive optical element are obtained by using an iterative Fourier transform analysis method, so that the diffractive optical element can reduce the optical diffraction effect when light passes through the corresponding transparent display screen, and further the image quality is improved.

Drawings

Fig. 1 is a flowchart of a method for manufacturing a diffractive optical element according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of an optical path of an optical system under a screen according to a first embodiment of the present invention.

Fig. 3 is a schematic diagram of an optical path of an optical system under a screen according to a second embodiment of the present invention.

Fig. 4 is a schematic plan view of a diffractive optical element according to an embodiment of the present invention.

Fig. 5 is a schematic plan view of a transparent display panel according to an embodiment of the present invention.

Description of the main elements

Underscreen optical system 100

Diffractive optical element 10

Substrate 12

Physical unit 14

Transparent display screen 20

Pixel unit 22

Optical module 30

Projected surface 40

The following detailed description will further illustrate the invention in conjunction with the above-described figures.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. When an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Referring to fig. 1, an embodiment of the invention provides a method for manufacturing a diffractive optical element, which is used to obtain structural information of a physical unit on a surface of the diffractive optical element and manufacture the diffractive optical element according to the structural information of the physical unit. A Diffractive Optical Element (DOE) is used to be placed on one side of the display to counteract or mitigate diffraction-induced speckle.

The preparation method of the diffraction optical element mainly comprises the following steps:

s1: a two-dimensional screen penetration distribution map is obtained, and a random phase is added to obtain a first spatial domain.

Specifically, referring to fig. 2 to 5, the diffractive optical element 10 is required to be attached to or disposed adjacent to one side of the transparent display 20, and the two-dimensional screen transmission distribution graph is a distribution graph of the light transmission rate of each microstructure of the transparent display 20. And adding a random phase to the obtained two-dimensional screen penetration distribution map to obtain a first spatial domain omega.

Further, the two-dimensional screen penetration distribution map is obtained by photographing the transparent display screen 20 with a backlight microscope.

S2: the first spatial domain is converted into the frequency domain by a fourier transform.

Specifically, the formula on which the fourier transform is performed is:

where ξ is the frequency domain, i is the imaginary number, and ω is the spatial domain.

It will be appreciated that the conversion from the first spatial domain to the frequency domain may be accomplished according to a fourier transform formula.

S3: higher order diffraction in the frequency domain is reduced by low pass filtering.

Specifically, the frequency domain is processed through a low-pass filter to reduce or eliminate higher-order diffraction in the frequency domain, and the influence of the higher-order diffraction effect on the performance of the diffractive optical element is reduced.

Further, the formula for reducing higher order diffraction by low pass filtering is:

where (x, y) is the coordinate of the frequency domain in the frequency space, and σ is the standard deviation of the normal distribution.

It is understood that the low-pass filter is a two-dimensional normal distribution, and the center of the low-pass filter is placed at the center of the frequency domain and then multiplied by the frequency domain to filter out the high-order diffraction.

S4: the low-pass filtered frequency domain is converted into a second spatial domain by an inverse fourier transform.

Specifically, the formula on which the inverse fourier transform is performed is:

the low-pass filtered frequency domain is re-converted to a new spatial domain by performing an inverse fourier transform, and is a second spatial domain distinct from the first spatial domain.

S5: determining whether the frequency component of the second spatial domain converges within a predetermined cut-off frequency, if yes, performing step S7; if not, step S6 is executed.

Specifically, the frequency component of the second spatial domain is the peak value of the frequency domain; the predetermined cutoff frequency is usually the cutoff frequency of the low-pass filter, and the specific value is the standard deviation σ of the normal distribution.

S6: a random phase is added to the second spatial domain to convert the second spatial domain into a new first spatial domain, and step S2 is performed.

Specifically, the frequency component of the second spatial domain does not converge into the cutoff frequency, that is, it is considered that the high-order diffraction filtering of the spatial domain is incomplete, and a next iteration is performed, that is, a new random phase is added to the second spatial domain to obtain a new first spatial domain, so that the step S2 is returned, and the next high-order diffraction filtering is performed through fourier transform, low-pass filtering, and inverse fourier transform.

S7: and converting physical unit parameters of the diffractive optical element according to the second spatial domain, and processing physical units on the substrate by using wafer level processes (WLO) according to the physical unit parameters to obtain the diffractive optical element.

Specifically, the formula for converting the second spatial domain into the physical unit parameters of the diffractive optical element is as follows:

Φ＝2π(n₀-n)d/λ；

where Φ is the spatial domain phase, derived from the spatial domain ω, n₀The refractive index of air, n the refractive index of the material of the diffractive optical element, d the depth of the structure of the physical unit, and λ the wavelength.

Specifically, the refractive index of air is generally 1; in some embodiments, the wavelength λ is 940.0 nm.

It can be understood that the structural depth of the physical unit can be obtained by substituting the second spatial domain and the plurality of parameters into the formula, and the number of the physical units can also be a plurality of corresponding units because the screen has a plurality of pixel units. And processing the physical units on a substrate by using a wafer-level process according to the obtained parameters of the physical units so as to obtain the diffractive optical element, wherein the diffractive optical element is matched with a screen for use.

It can be understood that the method uses an iterative fourier transform analysis method to process the spatial domain, and the purpose of multiple iterations is to filter the high-order diffraction point by point, and if the high-order diffraction is filtered to within the cutoff frequency once, the filtering effect is poor, and the reduction effect on the high-order diffraction cannot be completely matched with the pixel unit of the screen. Through a plurality of iterations, the high-order diffraction is gradually filtered out until the frequency component of the second spatial domain converges into the cut-off frequency, and then the spatial domain with better high-order diffraction filtering condition can be obtained, so that the converted physical unit parameters are more accurate, and the high-order diffraction reduction effect corresponding to the diffractive optical element is better.

Referring to fig. 2 to 5, an embodiment of the invention also provides a diffractive optical element 10, which includes a substrate 12 and a plurality of physical units 14, wherein the physical units 14 are disposed on at least one side of the substrate 12 by a wafer level process.

The diffractive optical element 10 is disposed corresponding to a transparent display 20 for reducing high-order diffraction and improving image quality. The diffractive optical element 10 can be, but not limited to, first, second, fourth, or eighth order, and the diffraction efficiency is multiplied as the order increases.

Further, the material of the substrate 12 may be glass or resin, but is not limited thereto.

Further, the substrate 12 is square and is used to fit the transparent display 20 with a suitable shape or other optical modules under the corresponding screen. It will be appreciated that as the shape of the transparent display 20 changes, the diffractive optical element 10 will need to change accordingly.

Furthermore, the length range of the side length of the square substrate 12 is preferably 1mm-3mm, and in the length range, the square substrate is well adapted to light source elements such as the transparent display screen 20 or a lens under the screen and a laser emitter, so that a good high-order diffraction reduction effect can be obtained.

The physical unit 14 is a microstructure processed on the substrate 12 by a wafer level process, and after the light passes through the physical unit 14, the physical unit 14 reduces high-order diffraction of the light, so that the image effect is better.

Specifically, the parameters of the physical unit 14 are obtained by the above-described diffractive optical element manufacturing method, and the physical unit 14 is processed on the substrate 12 by processing the substrate 12 by the parameters of the physical unit 14 obtained by the iterative fourier transform analysis method.

Further, the structural depth of each physical unit 14 is preferably in the range of 0.2 μm to 1 μm, in which the physical unit 14 has a good high-order diffraction reduction effect without excessively affecting the normal propagation of light.

Further, the line width of the physical unit 14 is preferably in the range of 0.5 μm to 4 μm, and in this range, the pixel unit 22 in the transparent display screen 20 can be well matched, and the corresponding higher-order diffraction reduction effect is more accurate.

It will be appreciated that the physical unit 14 is extremely small and there are inevitable deviations in the prior art process. In the present embodiment, the substrate 12 is processed by a wafer level process, and the processing accuracy can be within a range of ± 1.5 μm. Within this range, the high-order diffraction reduction effect on the transparent display screen 20 can be better satisfied.

In one embodiment, the diffractive optical element 10 is a second-order design, the minimum line width of the physical unit 14 is 3.1677 μm, the structural depth is 0.94 μm, and the corresponding transparent display 20 is an OLED (Organic Light-Emitting Diode) display.

Referring to fig. 2 and fig. 3, an embodiment of the invention provides an optical system 100 under a screen, which includes the diffractive optical element 10, the transparent display 20, and the optical module 30.

The transparent display panel 20 includes a plurality of pixel units 22 for periodic arrangement; the optical module 30 is used for receiving the light beam from the transparent display 20 or emitting the light beam outwards through the transparent display 20. The diffractive optical element 10 is disposed between the transparent display panel 20 and the optical module 30 or covers a side of the transparent display panel 20 facing the optical module 30.

Specifically, fig. 2 shows a receiving system, in which the optical module 30 is a CCD (Charge-coupled Device) camera, and is used for receiving light passing through the transparent display screen 20 and performing imaging according to the received light. The diffractive optical element 10 is covered on one side of the transparent display screen 20 and is used for reducing the optical diffraction effect of light rays passing through the transparent display screen 20.

Specifically, fig. 3 shows an emission system in which the underscreen optical system 100 further includes a projected surface 40. The optical module 30 is a Laser emitter, and is configured to emit Laser light through the transparent display screen 20, and may be a Vertical-Cavity Surface-Emitting Laser (VCSEL). The diffractive optical element 10 is covered on one side of the transparent display screen 20 and is used for eliminating the optical diffraction effect of the laser light passing through the transparent display screen 20. The light emitted from the optical module 30 passes through the diffractive optical element 10 and the transparent display 20, and is finally projected onto the projection surface 40.

Further, the transparent display screen 20 may be a plasma display screen, a Liquid Crystal Display (LCD), a Light Emitting Diode (LED), an Organic Light Emitting Diode (OLED), and the like, and is used for displaying application images, supplementary lighting, and the like, and may also be any other display screen according to actual requirements. The transparent display 20 may also include a touch function, for example, a capacitive touch electrode is disposed in the middle of the transparent display 20 to serve as an input device for human-computer interaction.

It can be understood that, since the size of the transparent display 20 is usually significantly larger than the size of the optical module 30, the size of the diffractive optical element 10 only needs to correspond to the size of the optical module 30. Whether the optical module 30 is used for transmitting or receiving, the side length range of the rectangular diffraction optical element 10 is within 1mm-3mm, and the optical path covering the optical module 30 can be realized.

Further, the range of the gap between the diffractive optical element 10 and the transparent display 20 is preferably 0 μm to 5 μm, and in this range, the diffractive optical element 10 can achieve a good effect of reducing higher-order diffraction.

An embodiment of the present invention also provides an electronic device (not shown) including a main body and the optical system 100.

The electronic device may be a smart phone, a tablet computer, a desktop display, a television, a Portable Multimedia Player (PMP), an electronic book reader, a notebook computer, a digital still camera, or the like.

According to the diffractive optical element 10, the preparation method thereof, the under-screen optical system 100 with the diffractive optical element 10 and the electronic device provided by the embodiment of the invention, the parameters of the physical unit 14 of the diffractive optical element 10 are obtained by using an iterative Fourier transform analysis method, so that the diffractive optical element 10 can reduce the optical diffraction effect when light passes through the corresponding transparent display screen 20, and further the image quality is improved.

Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention. Those skilled in the art can also make other changes and the like in the design of the present invention within the spirit of the present invention as long as they do not depart from the technical effects of the present invention. Such variations are intended to be included within the scope of the invention as claimed.